U.S. Pat. No. 2,657,195 broadly discloses polyesters of various stilbenedicarboxylic acid isomers with glycols, aminoalcohols, and diamines. Various glycols are disclosed containing 2 to 16 carbon atoms.
U.S. Pat. No. 3,496,839 relates to low molecular weight homopolymers of 4,4'-stilbenedicarboxylic acid and aliphatic glycols useful in radiation-cured crosslinked polyester coatings. 1,6-Hexanediol is disclosed in Column 2, lines 20 to 44, in a general listing of the glycols useful in these coatings. Neither U.S. Pat. No. 2,657,195 nor U.S. Pat. No. 3,496,839 distinguishes one stilbenedicarboxylic acid isomer from another, i.e., 4,4'- from 3,3'- or cis- from trans-, etc.
Our own U.S. Pat. No. 4,420,607, U.S. Pat. No. 4,459,402, U.S. Pat. No. 4,468,510 and U.S. Pat. No. 4,526,822 all disclose polyesters based on trans-4,4'-stilbenedicarboxylic acid using various glycols which include 1,6-hexanediol.
Other patents which dislcose trans-4,4'-stilbenedicarboxylic acid are Japanese Kokai No. 72348/74, and U.S. Pat. Nos. 2,657,194, 3,190,174, 3,247,043, 3,842,040, 3,842,041, and 4,073,777. Polyesters of trans-4,4'-stilbenedicarboxylic acid and neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, and 1,10-decanediol are disclosed by Meurisse, et al., in the British Polymer Journal, Vol. 13, 1981, page 57 (Table 1). Jackson and Morris disclose homopolyesters from trans-4,4'-stilbenedicarboxylic acid and various aliphatic glycols in the Journal of Applied Polymer Science, Applied Polymer Symposia, 41, 307-326 (1985). Our copending applications entitled, "Polyesters of trans-4,4'-Stilbenedicarboxylic Acid, 1,6-Hexanediol, and 1,4-Cyclohexanedimethanol" "Polyesters of trans-4,4'-Stilbenedicarboxylic Acid, 1,4-Butanediol and 1,6-Hexanediol", and "Polyesters of trans-4,4'-Stilbenedicarboxylic Acid, Ethylene Glycol and 1,6-Hexanediol" also are of interest.
Japanese Kokai No. 72348/74 referred to on page 1 discloses that 4,4'-stilbenedicarboxylic acid polyesters having I.V.s of 0.2 to 2.0 could be used to make blends with poly(butylene terephthalate), but only I.V.s of less than 0.9 were exemplified. Therefore, there is no suggestion of the unexpected properties of the present invention.
Insofar as we are aware, the art does not disclose unexpected properties of polyesters of trans-4,4-stilbenedicarboxylic acid and 1,6-hexanediol having inherent viscosities (I.V.) above 0.9. We have surprisingly found that such polyesters having I.V.s of at least 1.20 have exceptionally low melt viscosities at these high molecular weights and unexpectedly high tensile strengths when injection molded. The low melt viscosities at high I.V. (hence, high molecular weight) are very desirable from a processability standpoint.